1. Field of the Invention
The invention relates to machine tools for machining rotating workpieces and in particular to machine tools for machining rotating workpieces to have a non-cylindrical surface profile.
2. Review of the Prior Art
In a conventional machine tool, a tool is mounted on a tool holder which is carried on a slide moved by an electric motor via a lead screw. Such machine tools are capable of applying a wide range of cutting forces to a wide variety of workpieces.
It is a disadvantage of such conventional machine tools, however, that the inertia of the slide and the construction of the transmission by which the drive is transmitted from the motor to the slide limits severely the speed at which a rotating workpiece can be machined when the position of the tool has to be altered during machining. This is because, as the rotational speed of the workpiece is increased and/or as the speed of tool movement is increased, there is a speed at which the slide cannot react sufficiently quickly to positioning signals, so that the tool is not in a required position at a required time and so that the required profile is not machined. This is particularly true when the tool position is to be altered incrementally within a revolution of the workpiece or between revolutions.